Plastic bag zipper closure with sealing projections

ABSTRACT

A plastic bag comprising a welded segment at its closure which comprises sealing projections and interlocking projections to form a high integrity seal at the closure edges.

FIELD OF THE INVENTION

The present invention relates to plastic bags for storage such as foodand other storage bags having a zipper-type closure.

BACKGROUND

Plastic storage bags having zipper-type closures are known in the artand generally provide adequate closing function; but there is a risk ofleaking where the far left side of the zipper and the far right side ofthe zipper intersect the left and right side edges of the bag. Oneapproach to address these leaking concerns has been to ultrasonicallyweld the zipper profiles prior to heat welding for side sealing of theoverall edge. This approach is based on a thinking that the heat weldingalone used for the side sealing has insufficient sealing capacity toseal the zipper profiles, which are much thicker than the side wallsaway from the zipper profiles. The ultrasonic welding of the zipperprofiles at the bag edges involves pressing the profiles together andvibrating with ultrasonic energy. The resulting vibration frictiongenerates heat which melts the plastic so that it welds together. Thereis a continued desire and need to improve on this and other designs.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a plastic bagwith a zipper-type closure which can hold liquid and does not tend toleak where the zipper profiles intersect the side edges.

Briefly, therefore, the invention is directed to a plastic storage bagcomprising two panels which define a bag interior, the plastic bagcomprising: a first panel; a second panel, the first panel and secondpanel defining a bag interior and an opening at a top end margin of thefirst and second panels to permit access to the bag interior; the firstpanel and second panels being sealed to each other along bottom edgeremote from and parallel to the top end margin, and being sealed to eachother along a left edge and a right edge which are opposite from andparallel to each other and perpendicular to the bottom edge; and aclosure at the opening comprising mutually interlocking profiles on thefirst and second panels, respectively, the interlocking profilescomprising: a male profile on the first panel and a female profile onthe second panel directly opposite the male profile; the male profilecomprising an interlocking projection for engaging the female profile,wherein the interlocking projection extends perpendicularly from thefirst panel; the female profile comprising a channel for receiving theinterlocking projection of the male profile, wherein the channel isarcuate in cross section and comprises a base section attached to thesecond panel and a two arcuate arms which extend away from the base anddefine the arcuate channel; and sealing projections on the first paneladjacent to and on each side of the male interlocking projection;wherein the sealing projections taper from a thicker cross section at asealing projection base section attached to the first panel to thinnercross section at an end remote from the sealing projection base section;wherein the sealing projections are curved inwardly toward the base ofthe female profile where the female profile projects from the secondpanel.

The invention is also directed to a method for forming a plastic bagcomprising welding a segment of the male profile to an end segment ofthe female profile of the aforementioned bag wherein said welding formsa welded segment at left and right edges of the closure.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic fragmentary elevation of a bag;

FIG. 2 is a schematic elevation of a male closure profile being appendedto the bag;

FIG. 3 is a schematic elevation of a female closure profile beingappended to the bag;

FIG. 4 is a schematic elevation showing the closure profiles pressedtogether;

FIG. 5 is a schematic fragmentary elevation of the bag indicating edgeareas encompassing closure profile segments to be welded;

FIG. 6 is a schematic elevation showing the closure profiles weldedtogether;

FIG. 7 is schematic fragmentary elevation of an alternative bag with theclosure profile defining the top edge, and for use in connection with aslider mechanism;

FIG. 8 is an end elevation of the slider; and

FIG. 9 is a photograph of a welded closure area of a bag according tothis invention.

Corresponding features are given corresponding reference numeralsthroughout the drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention is directed to a plastic bag which comprises two abuttingflat panels having an opening at one edge and sealed along other edges,such as two rectangular panels sealed along three edges with an openingat the fourth edge. In one preferred embodiment, there is a first paneland a second panel, wherein the first panel and second panel define abag interior and an opening at an end margin of the first and secondpanels to permit access to the bag interior. These are shown in thefront view in FIG. 1 as two rectangular panels 5, 6, sealed along threeedges 7 with an opening at the fourth edge 10. For purpose ofillustration only, the lower left corner of first panel 5 is shownremoved in phantom so that second panel 6 is visible. There is azipper-type closure 4 shown schematically at the opening.

In one preferred embodiment, the closure 4 comprises first and secondmutually interlocking profiles designated 11 and 12 in FIGS. 2-4, whichis an end view of the closure showing the closure in cross section.These are appended to the first and second panels 5 and 6, respectively.The interlocking male profile 11 projects perpendicularly from the firstpanel 5 and has an interlocking projection 14 which comprises a bulbousend section 18 and a base section 16 which projects out from the panel.Male profile 11 also includes sealing projections 20 on the first panel5 adjacent to and on each side of the male interlocking projection 14.

The female profile 12 in FIG. 3 comprises two arcuate arms 26 and 28which extend away from the base and define an arcuate channel in thespace between the arms. This channel is sized and shaped receiving theinterlocking projection 14 of the male profile. The arcuate armscomprise a base section attached to the second panel and have inwardlyprojecting shoulders 36 which grip outwardly projecting shoulders 38under the bulbous tip of the male interlocking projection 14.

The sealing projections 20 of the male profile above and below theinterlocking extension taper from a thicker cross section at a sealingprojection base section 22 attached to the first panel to thinner crosssection at a tip end 24 remote from the sealing projection base section22. The sealing projections are curved inwardly over the interlockingprojection 14 and toward the base 30 of the female profile where thefemale profile projects from the second panel. The sealing projections20 project a distance from the first panel which is at least as great asa distance which the female profile projects from the second panel.

As can be seen in FIG. 4, as the profiles are pressed together, thetapered tips 24 of the sealing projections 20 tuck in underneath thearcuate arms of the female profile.

Turning now to FIG. 5, there is highlighted an area marked A whichencompasses a segment of the interlocking profiles which intersects theedge of the bag. In manufacturing the bag, the interlocking profiles arepressed together in this area of the bag and are welded together in amanner such that at least the tip segments 24 of the sealing projections20 which are tucked under the arcuate arms 26/28 are partially meltedsuch that they bond to the arms and form a liquid-tight seal at the sideedge in the area A. In various embodiments, the degree of meltingvaries. Melting can be imparted to part or all of the sealingprojections 20, as well as the arcuate arms 26/28, base 30, part or allof the interlocking projection 14, and even part of panels 5 and 6. Forexample, in one embodiment, the sealing projections projecting from thefirst panel are welded to the second panel and/or to the arcuate arms tocreate a seal at the left edge and right edge of the bag. The closurearea at the other edge the bag opposite from side A is welded in thesame manner. The sealing projections 20 project a distance from thefirst panel which is in one embodiment the same as a distance which thefemale profile as defined by the height of the arcuate arms 26/28project from the second panel. In particular, the height H₁ of thesealing projections shown in FIG. 2 is the same as the height H₂ of thereceiving channel arms shown in FIG. 3. In other embodiments, the heightH₁ is between about 75% and 100%, such as between about 80% and 90%, ofthe height H₂. As a general proposition, in one embodiment, the heightH₁ of the sealing projections is between about 0.035 and about 0.055inch; the width of projection 20 at its base 22 is between about 0.006and about 0.012 inch; the distance between sealing projection 22 andinterlocking projection 14 at their bases on the panel is between about0.02 and about 0.03 inch; the height of interlocking projection 14 isabout 0.02 to about 0.04 inch; the width of the bulbous section 18 atits widest point is about 0.02 to about 0.03 inch; the height H₂ whichthe arcuate arms project out from the second panel is between about 0.04and about 0.06 inch; the width of the female profile at its base, i.e.,from the outer edge of arm 26 to the outer edge of arm 28 is betweenabout 0.01 and about 0.02 inch; and the width of the female profile atits widest point between the outer edges of arms 26 and 28 is betweenabout 0.04 inch and about 0.05 inch. These are the dimensions when theclosure is as shown in FIGS. 2 and 3, prior to pressing and welding ofthe respective profiles together. Upon pressing and welding, several ofthe dimensions change such as the height of the sealing projections andof the arcuate arms.

In one embodiment, the male and female profiles are joined together inarea A by pressing followed by ultrasonic welding. As shown in FIG. 2,the sealing projections 20 are biased inwardly to almost overhang theinterlocking projection 14. That inward bias causes the sealingprojections 20 to tuck under the arcuate channel when the profiles arepressed together, as shown in FIG. 4. With the profiles pressed togetheras shown in FIG. 4, ultrasonic welding cis performed at the side edges Ain FIG. 5. The ultrasonic welding can be performed, for example, by useof ultrasonic welding equipment available from Shantou Xinda UltrasonicEquipment Co., Ltd. Exemplary conditions are frequency of 2 amplitude,temperature of 80-120° C., energy of 220V at 60 Hz, weld time of 15seconds; hold time of 8 seconds, and delay of 10 seconds. Afterultrasonic welding the profiles together, the three edges 7, 8, and 9 ofthe bag are heat welded together, which includes heat welding theprofiles in the area of A, using standard conditions that are used toseal panels together in forming bag edges. FIG. 6 shows the profilesafter welding, with the “rabbit ear” shaped sealing projections 20having been melted slightly during the side sealing process and therebymelded with the arcuate arms 28 of the female zipper profile and/or bagwall 6 to further secure against leakage. The shoulders 36 on thearcuate arms 26 and 28 grip outwardly the projecting shoulders 38 underthe bulbous tip of the male interlocking projection 14.

The width of the weld of the profile from the edge of the bag toward themiddle of the bag is typically between about 2.5 mm and about 5.0 mm,such as between about 3 mm and about 4 mm in width.

The zipper profile material is manufactured from, for example, LDPE,LLDPE, HDPE or PP. In such embodiments, the Shore D hardness of thezipper material is greater than about 45, such as between about 45 andabout 85. The bag panels 5, 6 can be made from any suitable materialincluding typically LDPE and LLDPE, or optionally another polyolefinsuch as HDPE, PP, etc.

In the primary embodiment shown in FIG. 1, the plastic bag of theinvention is closed by the user's fingers sliding along the closure fromleft to right or right to left, pinching the profiles together. In analternative embodiment, the plastic bag employs a slider such as isknown from US Pub. 2016/0031609. In this slider arrangement, the closureis at the top edge opening 10′ of the bag as shown at 4′ in FIG. 7, withthe front panel, rear panel, and side edges shown at 5′, 6′, and 7′,respectively. The closure 4′ is used in combination with a slider 30shown in FIG. 8. As shown in the top view in FIG. 8, the slider has aseparator or opener at 32 in the shape of a wedge and a constrictor orcloser at 34. The top edges of the closure profiles define rails shownat 11 and 12. Walls 35 hold the slider 30 on the rails of the closure4′. The separator 32 pushes the rails apart to unlock the closureprojections to open the zipper. And moving the opposite direction, thewalls 35 assist the constrictor 34 to push the closure profile closed.The slider 30 preferably has a shape, such as having differing walllengths, that allows it to be machine-sorted and machine-aligned in theproper direction during assembly. The constriction 34 illustrated hereextends inward from the walls 35 to define a narrower space than thewalls for closing the closure 4′. This is one example of a newer sliderconfiguration for illustration purposes only, and is not the only sliderconfiguration that will work with this variation of the invention.

In forming the bags, conventional methods are used. Most typically,blown film is coextruded with zipper profiles, and the films are thenaligned, sealed, and cut to form bags. Alternatively, it is possible toextrude the film and zipper profiles separately, and attach them to eachother in a separate process.

Example 1

Blown film and zipper profiles were coextruded and mating films werealigned, sealed, and cut to form bags. All components were made fromLDPE. The zipper profile components had the following dimensions, withreference to FIGS. 2 and 3: H₁ was about 0.043 inch; the width ofprojection 20 at its base 22 was about 0.009 inch; the distance betweensealing projection 22 and interlocking projection 14 at their bases onthe panel was about 0.024 inch; the height of interlocking projection 14was about 0.029 inch; the width of the bulbous section 18 at its widestpoint was about 0.025 inch; H₂ was about 0.049 inch; the width of thefemale profile at its base, i.e., from the outer edge of arm 26 to theouter edge of arm 28 was about 0.014 inch; and the width of the femaleprofile at its widest point between the outer edges of arms 26 and 28was about 0.048 inch. The coextruded zipper profiles on the panels areshown in FIG. 9. The profiles were then subject to ultrasonic welding atthe edges of each bag in the regions A shown in FIG. 5. The width ofeach welded area within region A was about 3 to 4 mm.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above products and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

1. A plastic bag comprising: a first panel; a second panel, the firstpanel and second panel defining a bag interior and an opening at a topend margin of the first and second panels to permit access to the baginterior; the first panel and second panels being sealed to each otheralong bottom edge remote from and parallel to the top end margin, andbeing sealed to each other along a left edge and a right edge which areopposite from and parallel to each other and perpendicular to the bottomedge; and a closure at the opening comprising mutually interlockingprofiles on the first and second panels, respectively, the interlockingprofiles comprising: a male profile on the first panel and a femaleprofile on the second panel directly opposite the male profile; the maleprofile comprising an interlocking projection for engaging the femaleprofile, wherein the interlocking projection extends perpendicularlyfrom the first panel; the female profile comprising a channel forreceiving the interlocking projection of the male profile, wherein thechannel is arcuate in cross section and comprises a base sectionattached to the second panel and a two arcuate arms which extend awayfrom the base and define the arcuate channel; and sealing projections onthe first panel adjacent to and on each side of the male interlockingprojection; wherein the sealing projections taper from a thicker crosssection at a sealing projection base section attached to the first panelto a pointed tip at an end remote from the sealing projection basesection; wherein the sealing projections are curved inwardly toward thebase of the female profile where the female profile projects from thesecond panel; wherein the sealing projections project a distance fromthe first panel which is at least as great as a distance which thefemale profile projects from the second panel; wherein the sealingprojections at their pointed tips are tucked under the outer surfaces ofthe female profile arcuate arms when the profiles are pressed together.2. The plastic bag of claim 1 wherein the female profile and the maleprofile extend from the left edge of the bag to the right edge of thebag.
 3. The plastic bag of claim 1 wherein the interlocking projectionof the male profile comprises a bulbous tip with outwardly projectingshoulders under the bulbous tip, and the arcuate arms of the femaleprofile have inwardly projecting shoulders for gripping the outwardlyprojecting shoulders under the bulbous tip of the male profileinterlocking projection.
 4. The plastic bag of claim 2 wherein theinterlocking projection of the male profile comprises a bulbous tip withoutwardly projecting shoulders under the bulbous tip, and the arcuatearms of the female profile have inwardly projecting shoulders forgripping the outwardly projecting shoulders under the bulbous tip of themale profile interlocking projection.
 5. The plastic bag of claim 2wherein the male profile and female profile comprise welded segments atwhich they are welded together at the left edge and right edge of thebag.
 6. The plastic bag of claim 2 wherein the male profile and femaleprofile comprise welded segments at which they are welded together atthe left edge and right edge of the bag.
 7. The plastic bag of claim 3wherein the male profile and female profile comprise welded segments atwhich they are welded together at the left edge and right edge of thebag.
 8. The plastic bag of claim 5 wherein the welded segments each havea width between about 2.5 and about 5 mm.
 9. The plastic bag of claim 6wherein the welded segments each have a width between about 2.5 andabout 5 mm.
 10. The plastic bag of claim 7 wherein the welded segmentseach have a width between about 2.5 and about 5 mm. 11.-15. (canceled)16. A method for forming a plastic bag comprising: welding a segment ofa male profile to an end segment of a female profile; wherein the bagcomprises: a first panel; a second panel, the first panel and secondpanel defining a bag interior and an opening at a top end margin of thefirst and second panels to permit access to the bag interior; the firstpanel and second panels being sealed to each other along bottom edgeremote from and parallel to the top end margin, and being sealed to eachother along a left edge and a right edge which are opposite from andparallel to each other and perpendicular to the bottom edge; and aclosure at the opening comprising mutually interlocking profiles on thefirst and second panels, respectively, the interlocking profilescomprising: said male profile on the first panel and said female profileon the second panel directly opposite the male profile; the male profilecomprising an interlocking projection for engaging the female profile,wherein the interlocking projection extends perpendicularly from thefirst panel; the female profile comprising a channel for receiving theinterlocking projection of the male profile, wherein the channel isarcuate in cross section and comprises a base section attached to thesecond panel and a two arcuate arms which extend away from the base anddefine the arcuate channel; and sealing projections on the first paneladjacent to and on each side of the male interlocking projection;wherein the sealing projections taper from a thicker cross section at asealing projection base section attached to the first panel to a pointedtip at an end remote from the sealing projection base section; whereinthe sealing projections are curved inwardly toward the base of thefemale profile where the female profile projects from the second panel;wherein the sealing projections project a distance from the first panelwhich is at least as great as a distance which the female profileprojects from the second panel; wherein the sealing projections at theirpointed tips are tucked under the outer surfaces of the female profilearcuate arms when the profiles are pressed together; and wherein saidwelding forms a welded segment at left and right edges of the closure.17. The plastic bag of claim 1 wherein each sealing projection isthickest at the sealing projection base section attached to the firstpanel and tapers to the pointed tip in a continual, gradual, andconsistent manner along its entire length.